Chris Hemsworth as Thor in the soon to be released Thor: The Dark World. We can become immersed in the fantasy because it looks believable and remarkable at the same time. Photograph: Marvel Studios/Allstar Picture Library

Marvel Comics revolutionised the superhero genre in the 1960s with comic book characters such as Spider-Man, Thor, Iron Man and the Hulk. Colourfully costumed adventurers who fought criminals and alien monsters primarily on the streets of New York City, and who, despite their incredible superpowers, struggled with personal and social problems. Stan Lee, the architect of the Marvel universe, routinely addressed readers as "true believers".

Almost 60 years later the same Marvel characters are making true believers of us all. The success of Marvel feature films over the last decade has moved superheroes from just an obsession of comic book fanboys to an international phenomenon. The superhero blockbuster trend shows no signs of slowing down, with upcoming releases of Thor: The Dark World, Captain America: The Winter Soldier, X-Men: Days of Future Past and dozens of other planned films, including the much-anticipated sequel to Avengers Assemble, and new television series such as Agents of S.H.I.E.L.D. Superheroes are everywhere, from shirts to toys to exhibitions like the Marvel Super Heroes 4D experience at Madame Tussauds.

The current dominance of superhero films at the box office can be attributed to a number of factors. The usual plot of an otherwise ordinary human gaining fantastic powers so that he (unfortunately rarely a "she") can vanquish his enemies and be adored by the masses will always be an appealing fantasy. Likewise, the metaphorical saving of major cities, be they New York, Metropolis or Gotham, is a comforting tale in a post-9/11 world. But the main reason that superhero films have become so popular in this millennium is because they can make us believe in the hero and in the spectacular action. Thanks to incredible advances in special effects, especially seamless incorporation of CGI images, live action superheroes finally look believable.

Successful superhero films used to be few and far between. The 1978 Superman and the 1989 Batman were undeniable blockbusters, but countless other attempts to bring superheroes to the big and small screen were embarrassing. Dolph Lundgren as the Punisher in a black T-shirt, Rex Smith as Daredevil in a black bodystocking and Reb Brown as Captain America in shiny spandex and a winged motorcycle helmet have been all but forgotten for a reason: they looked ridiculous.

The memorable tag line for Superman in 1978 was: "You will believe a man can fly." And while that film did offer a relatively good depiction of a live superhero, we never really believed he could fly. Viewers really had to suspend their disbelief for scenes of Superman flying among the skyscrapers with an adoring Lois Lane in his arms. Audiences may have been more forgiving of characters from the pages of DC Comics such as Superman and Batman because at least the films were a step up from the televised adventures of Superman in the 1950s embodied by George Reeves, and the campy 1960s take on Batman featuring Adam West. For the most part, live action superheroes looked like what they were: grown men playing dress-up in unflattering tights.

Seeing real people in unitards battling buffoonish supervillains robbed the genre of all the magic and fantasy that could be depicted on an illustrated page. In the comics, particularly those produced by Marvel, there was no limit to the type of stories that could be told. Giant, purple clad, planet-devouring monsters like Galactus could do battle with the Fantastic Four in the streets, or alien armies of Krees and Skrulls could be defeated by The Avengers. In comic books the only limitation was the artist's imagination. Film and television just could not compete with the fictional mise en scène of the comics.

But all that began to change in the dawn of the 21st century when The X-Men (2000) and Spider-Man (2002) franchises appeared as big-budget special effects masterpieces. Suddenly we believed not only that a human could fly, but that they could also shoot lasers out of their eyes, control the weather, pop "adamantium" claws out of their forearms, cling to walls and swing on spider webs through crowded streets.

Superb costuming, accomplished actors, and skilled directors such as Bryan Singer and Sam Raimi all played a part in finally elevating the genre of live-action superhero films from silly to exciting. But the biggest and most significant change was the believable CGI rendering of superpowers and super action. Hundreds of visual artists spent thousands of hours at their computers to create scenes that were realistic. Audiences were not confronted with the absurdity of a guy in a too-tight Spider-Man costume pretending to climb a wall. The action was realistic despite being pure fantasy.

The CGI rendering of Spider-Man swinging across rooftops was seamlessly interwoven with real actors and real cityscapes to the point that viewers would forget that during crucial scenes we were watching a computer-generated illusion rather than a real person. Film technology had reached a point where it could do what comic books had always been able to do, namely present a superhero story that is enhanced by fantastic images. Special effects had finally stopped being a distraction and started being an attraction.

There is a distinct cinematic pleasure in seeing bodies take flight, casting off the burdens of gravity, as when Tony Stark puts on the Iron Man suit and dashes off to fight bad guys. Or when Steve Rogers (Captain America) emerges from a body-changing experiment and immediately leaps through the city after a Nazi. Or when Thor soars into battle with his hammer at the ready. We can become immersed in the fantasy because it looks realistic, it looks believable and remarkable at the same time. As special effects showcases, superhero movies crystallise our childlike desire for cinema to be larger than life, to be spectacular.

Ask people of a certain age what they remember most about movies as a kid and they will tell you about the thrill of seeing a gargantuan star destroyer scroll across the screen at the beginning of Star Wars (1977); those a generation younger will fondly remember the first glimpse of the dinosaurs in Jurassic Park (1993). Children going to movies now will probably cherish the time they first saw Thor and the Hulk battling each other in The Avengers, or the newest Spider-Man fighting a giant lizard in The Amazing Spider-Man (2012). Superhero movies are no longer just childish, but they do offer childlike thrills to young and old alike.

Superhero movies can now show us things in motion that we could only have dreamed of before. No matter how dynamic a comic book is, it is still a static image that we have to imagine into action. In many ways the current crop of superhero films hark back to the earliest days of movie-making. The dawn of film is a period characterised by historians as "The Cinema of Attractions". The technology of motion pictures was so new and novel that people would pay to see almost anything because it was pure spectacle.

Galloping horses, men sneezing, trains pulling into stations, even an elephant being electrified were filmic spectacles, in the purest sense of the word, because they were something remarkable to see captured on film. Today's superhero movies may have more overwrought plots about good versus evil, but they appeal to our basic desire to see something spectacular. The believability of the characters and the action only makes the adventures all that more spectacular. If global box-office records and merchandising sales are any indication, the Marvel film universe has replicated what those comics did in the 1960s and made true believers of us all.

Jeffrey A Brown is associate professor at the department of popular culture, Bowling Green State University, Ohio